Dam construction.



L R. JORGENSEN. DAM CONSTRUCTION. APPLICATION FILED J NE 17, 1913;

Patented Feb. 17, 1914.

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DAM CONSTRUCTION. PPPPPPPPPPPPPPPPPPPP 17, 1913.

1,087,662. Patented Feb. 17, 1914.

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L. R. JORGENSEN. DAM CONSTRUCTION.- APPLICATION FILED JUNE 17,1913.

Patented 'Feb. 17, 191i 4 SHEETS-SHEET 3'.

L.R.JORGENSEN. DAM CONSTRUCTION.

APPLIOATION FILED JUNE 17,.1 913.

I 1,087,662, Patented Feb. 17, 1914.

4 SHEETS-SHEET 4.

UNITED STATES PATENT OFFICE.

LABS R. J'ORGENSEIL' 0F SOUTH BERKELEY, CALIFORNIA.

DAM CONSTRUCTION.

Specification of Letters Patent.

Patented Feb. 17, 1914..

Application filed June 17, 1913. Serial No. 774,242.

To all whom it may concern:

dams and more particularly to masonry dams of the arch type. In the single or multiple arch dams which heretofore have been constructed, it has been shown that there is a tendency for the arch to flatten out at its crown when under the load caused by the pressure of water against the convex side of the arch. The temperature and shrinkage stresses have also caused the fiattening of the arch at the crown, which, added to the deformation caused by the load, leaves this general type of dam open to two serious objections, first, non-coincidence between the center line of pressure and the axis of the arch; and, secondly, the transformation of radial stresses into cantaliver stresses. From the first of these causes there will be a tendency for the arch to buckle at the crown. The material necessary to prevent this buckling has never heretofore, to the best of my knowledge, been distributed in an economic manner, but to overcome these objections, masses of concrete and masonry have been distributed throughout the arch without regard to the particular necessity for more material at certain sections than at others.

One of the objects of my invention, there-- fore, is to overcome these objections and my invention consists essentially in constructing a dam in which the center line of pressure will substantially coincide with the axis of the arch when under load; the curvature of the dam being changed to bring about this result.

In addition to this, the invention consists of adding material to the crown of the arch which will resist any tendency for the arch to buckle at this point, due to the axial stresses.

Other objects of my invention will be hereinafter set forth and more particularly pointed out in the appended claims.

In the accompanying drawing in which my improved dam is illustrated, Figure l is a diagrammatic plan of a section of the dam showing the true circular arch in full lines and the improved arch being shown in dotted lines; Fig. 2 is a plan of the curved dam comprising a single arch; Fig. 3 is a vertlcal transverse section on the line 3- 3 of Fig. 2; Fig. 4 is a diagrammatic plan of a section of the arch on the line 1'718 of Fig. 6, showing the true circular arch in full lines, the improved arch being shown in dotted lines; Fig. 5 is a plan of a portion of a multiple arch dam; and Fig. 6 is a transverse vertical section on the line 1010 of Fig. 5.

In Fig. 2, I show a curved dam comprising a single arch designed in accordance with Patent No. 986,718, so that the angle subtended by the arch sections is constant or nearly constant for each of the horizontal sections of the arch. These arch sections have their curvature changed at points corresponding to the abrupt changes in contour IVIV IIIIII, etc.; the curvature' of each of the sections being a true circular are and having radii designated R", R etc. for

the up-stream face and corresponding radii struck from the same center for each of the respective down-stream faces.

Referring now to Fig. 1, a diagrammatic plan of a horizontal section is shown in full lines which has a correspondingly curved axis 4, 4; the middle third of the arch section lying within the lines 5, 5 and 6, 6 respectively. If it is assumed that the abutments are fixed and that the load is gradually thrown upon the dam structure due to the water pressure, this arch section will flatten out at the crown, which is explained by the fact that a stationary or concrete dam is not perfectly rigid, but is somewhat elastie and the deformation caused by the heavy load will necessarily occur at the crown or toward the crown as the abutments are fixed and rigid. Other'conditions thatjtcnd to flatten the arch at the crown are the temperature and shrinkage stresses which have an appreciable effect upon the curvature of a dam. As the load taken by a segment of an arch is directly proportional to its radius, the arch load is necessarily less at the flattened portions of the crown than at other portions of the arch, the center line of pres sure will deviate from the axis of the arch, resulting in a non-coincidence between the two which will cause a tendency for the dam to buckle at this point. Although this center line of pressure when the arch is under full load may still lie within the middlethird of the dam which is necessary for abthe shape of the arch, to make the axis of the dam coincide with the center line of pressure, the danger of buckling will be substantially eliminated. This will necessitate a change in the configuration of the up and down-stream surfaces of the arch from a. true circular arc to a curve such as a parabola, ellipse or other curve different from that of a true circle, depending upon the pressure and forces which act on the given arch section. This change in the configuration or contour of the arch is one of the important features of my invention and is determined in the following manner: The center line of pressure for a'true circular arch subtending the desired angle is determined in the usual way, by dividing each horizontal section into segmentsand then calculating the forces acting on each of the segments, After the pressure on each segment has been determined, a center line of pressure 7-7 is plotted; the distances which the pressure lines deviate from the axis of the arch section being shown by the distances marked a, b and c on Fig. 1 and for this particular arch section, the contour of the arch is then changed to bring about a coincidence between its axis and the center line of pressure which will result in re-designing the faces of the dam so that they will be curved in a manner different from that of a true circle as shown by the dotted lines 8--8 and 99. The new center line of pressure of this re-designed arch is then determined and if the coincidence between its pressure line and the axis is not sufiiciently close, then the same method may be repeated until the lines are substantially coincident. After this section of the arch has been determined, the same mode of procedure is followed in regard to the other horizontal sections lying between the different contours. This will result in the design of a dam with the upstream and down-stream faces of each respective arch section of difierent contour depending upon the relation between the pressure at the crown and at the abutments which does not remain constant for the various sections at different elevations. The dam is then constructed by superposing upon each other, arch sections of a contour shaped in accordance with the determined design, which will result in a dam whose up and down stream surfaces are warped; the contour of the surfaces of the different horizontal sections of the dam being elliptical, parabolical, or of some other curved surface, but the danger of the dam buckling ner, or in accordance with my Patent No, 986,718, it may be found that the lpwer sec-.' tions of the dam structure are overhung by the upper portions close to the abutments as shown in Fig. 2 and designated by reference character 0. This overhanging space should be filled out in such a way that there will be no over-hang, or in addition to eliminating .the over-hang, a small reverse curve may be provided so as to make a smooth junction between the arch and abutments, as is shown at f'in Fig. 2.

The second objection to the deformation or flattening 0fthe arch at and near the crown is the transformation of the radial stresses caused by the load Or water pressure acting on the true circular are into can-v taliver stresses. This, cantaliver action is nearly always amaximum at the crown and diminishes to zero at the abutments and will cause a tendency for the arch to buckle at its point of maximum value or at the crown. To offset this action, I add suflicient material, preferably on the down-stream side, which material not only provides resistance for the bending moment in the down stream direction (cantaliver action) but it also provides resistance for the shear due to this cantaliver action and stilfens the arch and prevents it from buckling in somewhat the same manner as the addition of material to the middle of a long column will prevent its buckling before the limit of compression is reached. This added material is shown in Figs. 2 and 3 and is designated D. A practical method of adding this material to the crown of the dam is to strike from a center 'fOr the down-stream face for each of the horizontal sections at a point lying farther down the stream than the point of the corresponding up-stream face, the distances between the two centers depending upon the magnitude of the bending moment or cantaliver action and the shearing stresses caused by this action. The material should preferably be added to. the dam before the shape of the circular arch has been re-constructed to bring the axis of the arch into coincidence with the center line of pressure, as the addition of this material will have an appreciable effect upon the position of the center line of pressure. With the addition of this material to a dam the contour of whose faces are curved to bring the axis into coincidence with the center line of pressure when the dam is under full load, the danger of the dam buckling at the crown or any other place is substantially eliminated. Moreover, the amount of material necessary to build such a dam is less than any other curved dam of suflicient strength to resistthe load without serious deformation of the structure which is due to the economic distribution of the material at the points where it is needed.

Referring now to Figs. at, 5 and 6, wherein I have shown a multiple arch dam constructed according to my invention. Buttresses 10 and 11 carry between them a sloping arch designated as an entirety by 12.. The upper end of the buttresses are joined together by braces 13, the ends of which are embedded in the concrete or masonry. Any suitable form of reinforcement may be used, as is shown at 14:. The construction thus far is of the general and well-known type and' need not be described in detail. In

multiple arch dams the up-stream faces of which are sloped, part of the weight of the arch will be carried by the arch section. This load caused by this weight is a maximum at the crown and decreases toward the abutments, due to the fact that the part of the arch wall adjacent the buttress runs substantially in the same direction as the buttresses themselves and therefore most of the weight of the arch at or near the abutments is carried directly by the buttresses. The weight components of the forces acting on the dam will, therefore, have their maximum values at the crown or points corresponding to those designated 15 and 17, and their minimum values at the buttresses or points designated 16 and 18. On the other hand, the load or pressure normal to the arch is not uniformly distributed over any given arch section but has a maximum value at the buttresses or the points corresponding to those designated 16 and 18, and a minimum at points 15 and 17. The latter is due to a difference in, elevation between the corresponding points of the arch section at the crown and at the buttresses, thebut-tresses being at a deeper elevation and hence subjected to a" greater load. There are therefore two different forces acting on each arch, one due to the weight and the other due to the pressure, which forceshave their maximum and minimum values oppositely disposed with respect to each other,'and will therefore partially counteract or tend to equalize each other when added together to give a more uniform total load. However, the forces are not entirely neutralized, for at the crest and toward the crest of the dam, forexample at the point 15, the weight component has. its smallest value and therefore the value of the total load will increase from the crown toward the abutments, the-load due to the pressure predominating. Upon the lower sections of the dam, the unbalanced load will be due chiefly to the weight component which increases more rapidly than the load, due to water pressure, so that at the point 17 the weight component predominates and therefore the total load will decrease from the crown toward the abutments. These two different forces acting on the dam will cause deformation or the flattening at different portions of the arch as the arch is not sufiiciently rigid to suffer strain without deformation. To eliminate the deformation and to prevent the arches from buckling, the contour of the arch sec-' tions should be changed in accordance with the method described in connection with Figs. 1 to 3, inclusive.

Referring now to Fig. 4, wherein is shown a diagrammatic plan of a. section on the line- 17' and 18' of Fig.6. The true circular arc is shown in full lines, the axis and middle third of the arch. being shown by the lines designated 21-21, 22-22 and 2323, respectively. The center line of pressure is determined by dividing the arch section into segments, as described in connection with Figs. 1 to'3, inclusive, and upon the determination of the center line of pressure of each segment the center line is plotted- This center line is shown in dotted lines in Fig. 4: and is designated 2 1-24. The contour of the up and down stream faces of the dam is then changed to bring about coincidence between'its axis and the center line of pressure'which is shown by the dotted lines 26-26 and 27 27, respectively.

Upon determining the center line of pressure in each of the different sections, it will be found that the center line of pressure deviates from the circular-axis of the arch in two directions. Through a section taken at the points marked 15 and 16 and points adjacent thereto, the pressure line will lie above the axis of the arch as is shown in Fig. 1; and, secondly, sections taken at the points marked 17 and 18 and adjacent there-.

to, the center line of pressure will fall below, as is shown in Fig. 5. The contours of the different arch sections are changed to arch will therefore have surfacesshap'ed in such a way that when the dam is under full load the center line of pressure for each of the sections of the archwill substantially coincide with the axis of the arch at any elevation. Material may be added to the crown of the arches of the dam to ofi-set the cantaliver action, as has been described in connection with Figs. 1 to 3, inclusive, the radii of the up and down stream faces of the arch being struck from difierent centers as has already been described.

Referring now to Fig. 5 wherein I have shown a construction of the buttresses which" intervals so that the load carrie has been found to give the best efiicienc for the smallest amount of material use A buttress is constructed with its upstream face at a substantially constant angle at about 60 with the horizontal. The downstream face, however, is changed at s acfid each of the sections of the buttres will be uniform. This down-streain face of the buttress will, therefore, be formed as shown in full lines in Fig. 5, the width of the buttresses being changed at the spaced intervals depending upon the forces acting on each section of the buttress which will decrease as the crest of the dam is reached. This construction is shown by the full line 19-20 Fig. 6. Instead of having an angular face, it is sometimes preferable to smooth off this surface into a curve such as is shown in the dotted lines 28-29.

Where a multiple arch dam is built across a creek or canyon, the buttresses should generally be arranged to straddle the deepest portion of the bed. As the canyon bed is substantially V-shaped below the buttresses, the most economical dam for this portion of the canyon would be one designed in accordance with my former Patent No. 986,718, each section of this portion of the dam having an up-stream radius corresponding to the width of the canyon at the various elevations and subtending a constant or nearly constant angle. This portion of the arch may be substantially vertical as shown in full lines and designated M in Fig. 6, but sometimes local conditions make it preferable to slope this portion, which construction'is shown in dotted lines at N. It may here be stated that the curva ture of the multiple arch dam is substantially constant from the crest to the foundation, as the difference in the distances between the buttresses at the top and bottom is negligible, and if it "were not for the changing of the contour of the arch to bring about coincidence between the axis and the center line of pressure, then the up-stream face of the arch between the buttresses would be cylindrical.

erable construction of a multiple arch for the deepest portion of a canyon or creek,

therefore, consists in the combination of a curved sloping arch. having a substantially constant radius between the buttresses and a portion extending below the buttresses, the sections of which have the curvature of their up-stream faces changed to correspond to the width of the canyon.

Referring again to Figs. 4 and 5, it is apparent that the portion of the sloping arch sections at the points marked 16 and 18 are subjected to greater water pressure or load than the points marked 15 and 17. For this reason the thickness of any arch should be increased from the crown where The 'prefmenace the thickness is represented by t on Fig. 4, to thickness T at the abutments. A section of the arch taken on any horizontal lane will therefore'show a substantially uniform thickness throughout from the crown to the abutments.

Having described my inventiomlclaim 1. A curved dam having the axis of curva-.

ture thereof at any elevation varying'from the curvature of a circle.

2. A curved dam having the axis of curvature thereof at any elevation substantially coinciding with the respective center line of pressure for that elevation when the dam is under full load.

'3. A curved dam, the axis of curvature thereof at one elevation thereof being substantially elliptical in contour.

4. A curved dam having a mass of ma-' terial for resisting the cantaliver action, said mass being of a maximum thickness at or near the crown and diminishing toward the abutments in a substantially horizontal direction, and being also of maximum thickness at the foundation and decreasing toward the crest.

5. A curved dam having curved up and down stream faces, the centers of curvature of which are non-coincident, the center of the down stream face being at a point farther down stream than the corresponding center of the up stream face, whereby sufiicient material is added to the dam to resist the cantaliver action. v

6. A multiple arch dam, each arch having warped up and down stream faces.

7. A multiple arch dam, each arch havin warped up and down stream faces, sai faces being inclined from a vertical plane. 8. A multiple arch dam, the axis of curvature of each arch at any elevation substantially coinciding with its corresponding center line of pressure when under full load.

9. A multiple arch dam, having sloping up stream faces, the axis of curvature of each arch at any elevation, substantially coinciding with its corresponding center line of pressure when under full load.

10. A multiple arch dam, having sloping up stream faces, each arch having some sections of the arch substantially elliptical in contour.

11. A multiple arch dam, having sloping up-stream faces, each arch having a horizontal section thereof substantially parabolical in contour.

12. A multiple arch dam, having sloping up-stream faces, each arch having one horizontal section of the arch substantially, elliptical and another section thereof substantially parabolical in contour.

13. A multiple arch dam having a buttress, the slope of the down-stream face of said buttress being changed at spaced intervals whereby the load will be substantially constant at any horizontal section-of the buttress.

14. A multiple arch dam, the thickness of each arch increasing from the crown toward the abutments.

15. A sloping multiple arch dam, having deepest portion of the canyon and an arch between the buttresses said arch having a 1 portion extending .below the buttresses, said portion comprising sections of varying radii corresponding to the width of the canyon, the radius of the arch between the buttresses being substantially constant;

17. A curved dam, having its up-stream face varying from the curvature of a true.

circular arc and material added to the dam to resist the cant'aliver action, said material having its maximum thickness at the foundation adjacent the crown. V

18. A curved dam, having its faces varying from the curvature of a true circular arc and material added to said dam to resist the cantaliver action, said material having its maximum thickness at the foundation adness toward the crest and abutments respectively 19. A multiple arch dam, having a sloping Lip-stream face the thickness of the arch increasing from the crown to the abutment.

20. A multiple arch dam, having a sloping up-stream face, the thickness ofv each arch increasing'from the crown to the abutment, said dam also including material added to the dam for resisting the cantaliver action, said material being of maximum thickness at the foundation adjacent the crown and diminishing in thickness towardthe abutments.

21. A curved dam for a canyon or the like, comprising buttresses straddling the deepest portion-ofthe canyon, and an arch between the buttresses having a portion extending below the buttresses, said portion comprising arch sections of varying radii corresponding to the width of the canyon, the radius of the arch between the buttresses being substantially constant, the center line of pressure of each section of the arch substantially coinciding with its corresponding center line of pressure when the arch is under full load.

- In witness whereof, I subscribe my signa ture, in the presence of two witnesses.

. LARS R. J ORGENSEN. Witnesses:

JAS. F. STRACHAN, HALFDAN ENKEBOLL. 

